A Study on 5G Millimeter Wave Channel: Measurements and 3D Ray-Tracing Simulations

Abstract

Wireless communication has achieved remarkable innovations and achievements in the history of wireless communication due to the spread of smart devices and the success of Long-Term Evolution (LTE) and Wireless Local Area Network (WLAN), the fourth generation (4G) mobile communication standards. Based on the success of 4G mobile communication, research on wireless communication is accelerating the research and standardization of the fifth generation (5G) mobile communication technology, the next generation mobile communication standard. 5G mobile communication research is moving toward overcoming of unprecedented communication experience and providing the best convenience of users. In particular, research on reliable communication techniques for increased connectivity due to an increase in the number of communication devices and for harsh environments such as maritime and underground tunnel, and high-speed mobile trains, has been attracting attention. In addition, there is a tendency to overcome the limitations of the deficient frequency use of the existing VHF and UHF bands and to utilize the millimeter wave frequency band in mobile communication to meet new demand. In this dissertation, the problems related to 5G mobile communication are predicted from the viewpoint of the wireless communication channel, and the solution is taken. First, I propose a wireless channel analysis and modeling method based on human body effect in indoor environment. In this chapter, I investigate propagation characteristics of indoor environment based on human body and surrounding environment by measuring channel characteristics in 3.5 GHz band and suggest channel models. The channel impulse response is measured through the wideband frequency response data in the 1.6 GHz bandwidth, and the number of rake fingers that can minimize the transmission bit error rate is suggested. Next, I measured the communication channel in the maritime environment. The maritime environment is highly dependent on wireless communication because of safety and high data demand, whereas research on maritime channel is limited. Conventional maritime communication systems are based on narrowband radio communication for telemetry or limited information transmission, and it was insufficient to transmit enough distress information at the time of an accident, which causes great loss of life and property. In this dissertation, I conducted a channel study for the offshore maritime environment through the measurement of sea channel in the West Sea. The channel parameters such as received signal strength, path loss, and received signal excess delay are measured through narrowband and wideband measurements. The existing ITU-R P.1546 model predicted the signal attenuation on the offshore surface by free space path loss. However, the measurement results show that the two-ray model considering the sea surface reflection wave, direct wave and antenna height is more accurate than the existing model. Finally, ray-tracing simulation method is developed to study the millimeter wave band channel and its applicability on cellular networks. The millimeter wave band has been used for limited services such as Local Multipoint Distribution Service (LMDS) and military communications systems, but it is now expected to be utilized as a new mobile communications frequency band to meet the soaring demand in recent years. Millimeter wave band is different from existing VHF and UHF bands, so it is essential to study channel for stable and efficient configuration of mobile communication network. Because of the intrinsic loss due to high frequency, most of measurements on millimeter wave uses directional horn antenna, which makes the measurement time-consuming and hard to obtain. The ray-tracing technique has been widely used as a simulation technique to complement the lack of real measurement data by implementing computer simulation of the propagation of radio waves. Through the comparison with the measured data, we implemented a ray-tracing simulator with proper performance for both line-of-sight and non-line-of-sight regions, and analyzed the coverage of the base station in the high-rise urban area. In addition, based on the currently used 4G base station location, I predicted the situation when introducing the 28 GHz band base stations on the same position of LTE base stations and suggested a modeling method of the probability of line-of-sight, non-line-of-sight, and outage.